Currently, the look, feel, and behavior of the user interface for some operating systems are integrated within the core of the operating systems itself. Changing the user interface, therefore, requires upgrading the operating system. However, there is a good reason to integrate the user interface very tightly with an operating system—it yields a high performance, stable, and robust user interface.
Typically, the user interface, like other aspects of an operating system, is exposed to applications through application programming interfaces (API's). In many operating systems, there are two types of memory, unprotected memory, such as what is known as user mode memory, and protected memory, such as what is known as kernel mode memory. Having protected memory helps ensure the stability and security of the operating system itself. Therefore, the API functions for features of the operating system, such as the user interface, are typically implemented within the protected memory.
There are many different existing approaches to changing the implementation of API's. The existing implementation may itself be changed. However, if these API's are implemented in kernel mode, the cost of developing, testing and debugging these changes can outweigh the benefit the new features provide. Kernel mode changes, in general, are not desirable. Furthermore, changing the implementation of an API can cause existing applications to stop working correctly, due to changes in behavior. This situation could adversely affect backward compatibility with previous versions of the operating system. Another approach is to introduce new API's, corresponding to new features and functionality. However, for the user interface in particular, this is an undesirable solution. Since most applications call many user interface API's, they would have to be significantly changed to utilize the new API's. Furthermore, customers may be required to upgrade their applications along with the operating system to take advantage of the new features and functionality. Other approaches have similar and additional disadvantages. For these and other reasons, therefore, there is a need for the present invention.